Verizon, AT&T or T-Mobile? And which modem is best for them?

To (someday) finalize my Librem 5 order I need some helping making a modem choice (i.e. band and frequency support) and a network choice (i.e. a cellular plan).

I’m not a network engineer and I’m not a cell phone expert either.

I live in rural California (USA) where Verizon has the best cellular coverage, followed by AT&T and T-Mobile, in that order.

I’m getting bogged down in all of the Jargon and various mode and band names.

I’m guessing what I’m shooting for is good LTE (“mode”) support hopefully with V0LTE over it. (BTW, is “mode” now called “interface” in modern parlance?) Also, I think there should be GSM and PCS support for fallback mode for voice?

As near as I can tell the BroadMobi BM818-A1 is the best modem for both Verizon, AT&T, and T-Mobile, but I’m not yet 100% sure???

What I think is true is that LTE superseeds both Verizon’s use of CDMA and AT&T’s use of GSM and EGSM, and has pretty good cell tower support by now. helps narrow bands down a bit with the region of “NAR” (the North America Region) using LTE bands:
2, 4, 5, 10, 12, 13, 14, 17. 23, 24, 25, 26, 27, 29, 30, 66, 70, 71, 74, 75, 76, and 85. But this is not of too much help. lists the 4 available Librem 5 modems: Gemalto PLS8-E & PLS8-US, and BroadMobi BM818-E1, & BM818-A1, and shows which modems support which GSM, HSPA and LTE bands.

For fallback mode (falling back from LTE), all four modems seem to support either:

  • GSM (the old European/global standard) or
  • EGSM (the newer GSM)


  • PCS (the old basic Personal Communications Service) or
  • DCS (Digital Cellular System, which I’m not really sure what this is).

Is this correct for fallback modes?

Also looking at the BroadMobi BM818-E1 it seems to be the modem which supports all needed LTE-FDD (Long Term Evolution - Frequency Division Duplex) bands for Verizon, At&T and T-Mobile, except B14, B29, B30, and B71:

Verizon: B2, B4, B5, B66, … B13,

AT&T: B2, B4, B5, B66, … B12, B14, B17, B29, B30

T-Mobile: B2, B4, B5, B66, … B12, B71

Near as I can tell

B14 is used only for emergency services
B29 is used for supplemental downlink
B30 is used for additional capacity (?? as an alternate channel??), and
B71 is an optional band, as it’s not yet used by many phones.

So none of these are critical.

Am I on the right path?

…Next is to figure out how to order ANY cellular plan from any any of these companies, as none of them list the Librem 5 as supported, or even acknowledge it’s existence. Any thoughts on this?

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I’ve been frequently for some time around rural California and played with major carriers, testing them,etc. Don’t waste your time, looking fur alternatives.
Just look at which modem has all/most of yoir (Verizon’s) bands and take that one. Nothing to overthink there.
Now, when you talk about fallback for voice. As of now , Verizon uses CDMA. But, in the late December, they will shut it down. That’s where we don’t have the clear answer yet. If the modem is certified by VZW you might be able to get the phone use VoLTE , if not - close to impossible. Why ? Verizon requires all phone manufacturers to submit their devices for full certification. once completed, all devices in the same line, get on their list, so the moment you pop the SIM in, Verizon recognizes it (IMEI number) and you are able to use VoLTE automatically. If device is not certified (L5 won’t be 4 long time) but modem is , you might be able to get it to work, by submitting a different IMEI. I’ve done it many times. And finally, if both modem and phone are not certified, you won’t stand a chance for this important feature. Best case , you’ll probably end up with internet only.
Still, we’ll have to wait and see from more testings and experiences. As promised, Purism will share that with us. And of course everyone in community, here. I expect to know that some time soon .

I use AT&T as my carrier. The GSM band’s they use are 850 + 1900. So the modem I’m picking is the Gemalto PLS8-US which support’s GSM band’s 850 , 900 , 1800 , 1900

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Something to think about, you might would want to cancel Verizon to switch a different carrier someday. I’ve known people had bad experiences with Verizon, even AT&T and T-Mobile. You might want to look into mobile virtual network operators, like Cricket, MetroPCS, Mint Mobile, etc, which are lot cheaper but they use bands under major carriers. So if you decided to switch to different carrier, would the same modem still work?

There’s discussion about choosing the right modem here.

Whenever I mention this elephant in the room, I get shushed. My MVNO is Republic Wireless and I use a Motorola G6 with LTE because that is what RW said would work on their T-Mobile/Sprint network coverage. But I still can’t get a carrier signal in my living room. Am I going to switch to Verizon or AT&T? I can make do with VoIP and poor cellular coverage.

I won’t buy a Librem phone until someone else reports success using it on Republic Wireless as a BYOP, even though I have a burning desire to deny The GOOG access to my location history and usage of Google Maps. But that won’t happen because RW has an Android app that makes VoIP work with cell service. Ooops. When will Purism support apps and low-level OS adaptations that make VoIP work? Haven’t heard a word about that.

Verizon and Sprint are both CDMA networks. A device will only work on their network if they allow it. Sprint customer service once told me that they would only allow devices that already had the name, “Sprint” stamped on them somewhere. AT&T & T-Mobile are open networks - if you can put your sim in the phone and connect it to their towers you can use their network.

Even if you get the, “right” modem for Verizon or Sprint it won’t work on their networks. Yes, you spoof the phone’s IMEI but that isn’t legal in all locations.

Thank you for your thoughts everyone!

Until someone demonstrates otherwise, Verizon and Sprint are non-starters. The way to go is with either T-Mobile or AT&T or both (via 2 sim cards).

Also today I found this helpful page on buying prepaid SIM cards.

So now I just need a modem that supports both T-Mobile and AT&T, and then I think I can buy a SIM card for either and see how it goes with that, … I think.

Looking up AT&T and T-Mobile in this Librem 5 carrier compatibility thread: seems to show pretty good support using the BM818-A1 modem. Only bands B14, B30, and B71 are not supported and none of them seems like a deal breaker. The other modems all have many significant missing bands.

So it looks like the modem question in the US for AT&T and T-Mobile is answered best with the BroadMobi BM818-A modem.


Good luck with ATT. My brother ever since moved to Rancho Mission Viejo (OC) , at his housekept missing calls, dropping calls,.no signal same with my phone once I switched (back) to Verizon, he saw that you can actually use the phone at home. switched in no time. What I’m saying, be careful. If you are using unlocked device , test out other networks where you live and areas of your commute and work.
When I originally switched to ATT , it was because I wanted this " freedom" to buy any device. What I found was the opposite. They certified less unlocked devices than VZW and have much smaller whitelist as well. I was forced to get rid of 2 factory unlocked Motorolas because no trick helped me have VoLTE. I started looking into forums and saw the same frustration everywhere.

ATT is not an “open” network.
Verizon is not a "closed " one neither.
Verizon has a bigger list of factory unlocked phones allowed to work than ATT. Most phones by major OEMs that are unlocked , GSM only and have right LTE bands will work on Verizon.
I don’t think you know what you are talking about here. I’ve spent years on both carriers.
And when I said to change IMEI , I didn’t mean “spoofing”, but asking CS Rep to register-assign a different IMEI for your SIM- line (can do it even before using your new phone) , so the system can activate this important feature VoLTE. They are all willing to help and some even know about the trick. With most devices it works on Verizon. On Att not so much.

For Verizon, it may be helpful to activate the SIM card in a Verizon-locked phone before using it in the Librem. If not, I’m sure T-Mobile or any MVNO would be happy to take my business instead.

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@Jt0, thanks for the interesting idea. I don’t have any smart phone to do this with. So at least for me this remains an idea of last resort in the future.

@Tatatirci, Thanks for your insight about Verizon, AT&T, and VoLTE! You’re right: I don’t know, which is why I’m asking here. I’ve already pre-ordered the Librem. Just figuring out what modem to get when the time comes.

In other words, I am planning on being a geninea pig, and finding out what will work, or not, but going at this as well informed as possible. Thank you again.


I agree with the general theme of this thread. I’m currently on Verizon with an old AT&T iPhone and constantly have to deal with the data on my phone going to 1x and losing data altogether. I’m trying to figure out the best course of action for when the time comes for me to choose a modem.

Will LTE work with only 1 working band ? I.E. my local tower supports 2,12,17

ATT wireless say for LTE they use B2 1900mhz and b5 850mhz

So band 2 1900mhz is the only frequency my tower supports that will work with att .

Does a device need or work better with multiple usable bands or should it work ok with 1 band .

The broadmobi certainly supports more bands but the Gemalto supports what ATT uses .


This can work out in some cases. In general, Verizon won’t make a difference in initial activation between Verizon branded (locked) device and Unlocked Certified device. This is the best first step to take, if device available. However, in many instances, the swap back to your uncertified phone, it defaults back to deactivated VoLTE. I had that happen more often than not. That’s, when you call the CS and ask for Tech Support and do the whole IMEI registration I talked about earlier

For now, I can only make uneducated guesses :slight_smile:
3 out of 3 is better than 1. Of course, that’s assuming that there is some altering done due to the traffic conditions. Also, what was brought years ago with AWS or something called like that, is that the some phones (Moto X among first) were able to enhance data transmission by merging traffic from 2 signals. Now, I can assume that that was some patented BS by Qualcomm , which may not be available on Gemalto and Broadmobi.

What I would focus on, is what areas of your commute are and look at the cellular map. I would worry more for those bands that are usually isolated and rarely mix in with the cluster of others. That’s what Verizon did with 13 & 66. Though, they are getting mixed in with the basic 2/4/5 in some urban areas, they were mostly used to replace CDMA in rural areas and stand alone there. That’s a deal breaker for folks traveling or living there. ATT probably didn’t have to that, since they’ve been GSM only for so long. I would still make sure they don’t have it set up like that.

If the modem is on a removable card instead on being soldered down, it would be easy to purchase a different modem if necessary after purchase of the phone, and to just swap out modems if necessary. Does anyone know if this is an option and if so, how much that second modem would cost?

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Only the BroadMobi BM818-A1 supports 2, 12 and 17.

In terms of the coverage, BM is way better for us in US. Now just to see if the get approved - certified by ATT & Verizon.

That’s something we have to wait for Purism to announce.